Abstract: The calculation study on the road capacity mainly focuses on the study on the correcting coefficients of the theoretical road capacity under the normal condition, but the effect of the stochastic factors on the road section on the practical capacity cannot be rechoned with, either. Therefore, the authors analyze the calculation method of the actual capacity of the road section, decide the various factors affecting the actual capacity and analyze their random. On this basis, by means of the flexibility in use of BP neural network, the easy understanding in method, and the good embodiment of the effect of random, the functional relationship between the influencing factors and the actual capacity is approached in the model so that the equation of fitting formula is obtained. According to the existing sample, the neural network model for the calculation of actual capacity is established and tested.